GROWTH OF GAN, INGAN, AND ALGAN FILMS AND QUANTUM-WELL STRUCTURES BY MOLECULAR-BEAM EPITAXY

GaN, AlGaN and InGaN films have been grown by molecular beam epitaxy ( MBE) using RF plasma sources for the generation of active nitrogen. Th ese films have been deposited homoepitaxially onto GaN/SiC substrates and heteroepitaxially onto LiGaO2 substrates. LiGaO2 is an ordered and closely-lattice-matched orthorhombic variant of the wurtzite crystal structure of GaN. A low-temperature AlN buffer layer is necessary in o rder to nucleate GaN on LiGaO2. Thick GaN and AlGaN layers may then be grown once deposition is initiated. InGaN has been grown by MBE at mo le fractions of up to 20% as a quantum well between GaN cladding layer s. The indium containing structures were deposited onto GaN/SiC substr ates to focus the development effort on the InGaN growth process rathe r than on heteroepitaxial nucleation. A modulated beam technique, with alternating short periods of (In, Ga)N and (Ga)N, was used to grow hi gh-quality InGaN. The modulated beam limits the nucleation of metal dr oplets on the growth surface, which form due to thermodynamic limitati ons. A narrow PL dominated by band edge luminescence at 421 nm results from this growth technique. Growth of GaN at high temperatures is als o reported.